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Kumaran S, Parthasarathy K. Cobalt(III)-Catalyzed Synthesis of Fused Quinazolinones by C-H/N-H Annulation of 2-Arylquinazolinones with Alkynes. European J Org Chem 2020. [DOI: 10.1002/ejoc.201901763] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Krishna S, Sathishkumar P, Pugazhenthiran N, Guesh K, Mangalaraja RV, Kumaran S, Gracia-Pinilla MA, Anandan S. Magnetically recyclable CoFe2O4/ZnO nanocatalysts for the efficient catalytic degradation of Acid Blue 113 under ambient conditions. RSC Adv 2020; 10:16473-16480. [PMID: 35498872 PMCID: PMC9052941 DOI: 10.1039/d0ra00082e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Accepted: 03/27/2020] [Indexed: 11/29/2022] Open
Abstract
CoFe2O4/ZnO magnetic nanocatalysts were synthesized using a low-frequency ultrasound-assisted technique to enhance the optical, morphological, magnetic and catalytic properties of ZnO. The as-synthesized nanocatalysts were characterized by XRD, Raman, TEM, DR-UV-Vis and VSM analyses in order to confirm the expected modifications of the resulting nanocatalysts. The Raman spectral analysis revealed substitutional Zn2+ in the CoFe2O4/ZnO nanocatalyst. The as-synthesized material was tested for its catalytic activity in the degradation of Acid Blue (AB113), a known textile pollutant. The CoFe2O4 and CoFe2O4/ZnO nanocatalysts revealed the efficient catalytic degradation of AB113 in ambient conditions. The nanocatalyst dosage and the initial concentration of AB113 were varied by fixing one parameter as constant in order to determine the maximum catalytic efficiency with the minimum catalyst loading for AB113 degradation. The CoFe2O4/ZnO nanocatalyst demonstrated 10-fold enhanced mineralization of AB113 compared to the individual bare nanocatalysts, which could be achieved within 3 hours of catalytic degradation of AB113. The magnetic CoFe2O4/ZnO nanocatalyst was found to be stable for six consecutive recycles of AB113 degradation, which indicates that the catalytic efficiency of the nanocatalyst was retained after various numbers of cycles. CoFe2O4/ZnO magnetic nanocatalysts were synthesized using a low-frequency ultrasound-assisted technique to enhance the optical, morphological, magnetic and catalytic properties of ZnO.![]()
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Kaur H, Kumaran S, Bhatia R, Chopra S, Nehra A. Effectiveness of homebased comprehensive neuropsychological rehabilitation for post stroke aphasia in limited resource settings: An fMRI based randomized controlled trial. J Neurol Sci 2019. [DOI: 10.1016/j.jns.2019.10.303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bhasin A, Srivastava P, Kumaran S, Pawan K, Mewar S. Bone marrow derived mononuclear stem cells in chronic stroke: Functional imaging & spectroscopic analysis. J Neurol Sci 2019. [DOI: 10.1016/j.jns.2019.10.811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Thayakaran R, Perrins M, Gokhale KM, Kumaran S, Narendran P, Price MJ, Nirantharakumar K, Toulis KA. Impact of glycaemic control on fracture risk in 5368 people with newly diagnosed Type 1 diabetes: a time-dependent analysis. Diabet Med 2019; 36:1013-1019. [PMID: 30848519 DOI: 10.1111/dme.13945] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/05/2019] [Indexed: 12/30/2022]
Abstract
AIMS To assess whether glycaemic control is associated with a lifelong increased risk of fracture in people with newly diagnosed Type 1 diabetes. METHODS People with newly diagnosed Type 1 diabetes between 1 January 1995 and 10 May 2016 were identified in The Health Improvement Network database. Longitudinal HbA1c measurements from diagnosis to fracture or study end or loss to follow-up were collected. A Cox proportional hazards model with HbA1c included as a time-dependent variable was fitted to these data. RESULTS Some 5368 people with newly diagnosed Type 1 diabetes were included. The estimated adjusted hazard ratio (aHR) for HbA1c was statistically significant [aHR 1.007; 95% confidence interval (CI) 1.002-1.011 (mmol/mol) and aHR 1.07; 95% CI 1.03-1.12 (%)]. An incremental higher risk of fracture was observed with increasing levels of HbA1c . CONCLUSIONS In people with newly diagnosed Type 1 diabetes, higher HbA1c is associated with an increased risk for fractures.
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Tiwari V, Nanda S, Mattoo B, Kumar U, Kumaran S, Bhatia R. Effect of rTMS therapy on pain descriptors and corticomotor excitability in fibromyalgia: a randomized control trial. Brain Stimul 2019. [DOI: 10.1016/j.brs.2018.12.620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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Cawley A, Golding S, Goulsbra A, Hoptroff M, Kumaran S, Marriott R. Microbiology insights into boosting salivary defences through the use of enzymes and proteins. J Dent 2019; 80 Suppl 1:S19-S25. [DOI: 10.1016/j.jdent.2018.10.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 10/23/2018] [Accepted: 10/25/2018] [Indexed: 10/28/2022] Open
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Rajiv S, Kumaran S, Sathish M. Long‐term‐durable anti‐icing superhydrophobic composite coatings. J Appl Polym Sci 2018. [DOI: 10.1002/app.47059] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Ananthakumar K, Kumaran S. Experimental Investigation and Prediction of Optimum Process Parameter for Plasma Assisted Diffusion Bonding of Commercial Pure Titanium and Austenitic Stainless Steel. ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2018. [DOI: 10.1007/s13369-018-3384-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Kumaran S, Tamil Selvan K, Justin Paul G, Swaminathan N. Temporal profile of AV nodal conduction block recovery pattern in acute inferior wall myocardial infarction following thrombolysis. Indian Heart J 2017. [DOI: 10.1016/j.ihj.2017.09.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Chopra S, Kumaran S, Sinha S, Kaur H, Nehra A. Using functional MRI to track neuroplasticity after cognitive rehabilitation post traumatic brain injury. J Neurol Sci 2017. [DOI: 10.1016/j.jns.2017.08.2670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Singh AK, Ekka MK, Kaushik A, Pandya V, Singh RP, Banerjee S, Mittal M, Singh V, Kumaran S. Substrate-Induced Facilitated Dissociation of the Competitive Inhibitor from the Active Site of O-Acetyl Serine Sulfhydrylase Reveals a Competitive-Allostery Mechanism. Biochemistry 2017; 56:5011-5025. [PMID: 28805060 DOI: 10.1021/acs.biochem.7b00500] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
By classical competitive antagonism, a substrate and competitive inhibitor must bind mutually exclusively to the active site. The competitive inhibition of O-acetyl serine sulfhydrylase (OASS) by the C-terminus of serine acetyltransferase (SAT) presents a paradox, because the C-terminus of SAT binds to the active site of OASS with an affinity that is 4-6 log-fold (104-106) greater than that of the substrate. Therefore, we employed multiple approaches to understand how the substrate gains access to the OASS active site under physiological conditions. Single-molecule and ensemble approaches showed that the active site-bound high-affinity competitive inhibitor is actively dissociated by the substrate, which is not consistent with classical views of competitive antagonism. We employed fast-flow kinetic approaches to demonstrate that substrate-mediated dissociation of full length SAT-OASS (cysteine regulatory complex) follows a noncanonical "facilitated dissociation" mechanism. To understand the mechanism by which the substrate induces inhibitor dissociation, we resolved the crystal structures of enzyme·inhibitor·substrate ternary complexes. Crystal structures reveal a competitive allosteric binding mechanism in which the substrate intrudes into the inhibitor-bound active site and disengages the inhibitor before occupying the site vacated by the inhibitor. In summary, here we reveal a new type of competitive allosteric binding mechanism by which one of the competitive antagonists facilitates the dissociation of the other. Together, our results indicate that "competitive allostery" is the general feature of noncanonical "facilitated/accelerated dissociation" mechanisms. Further understanding of the mechanistic framework of "competitive allosteric" mechanism may allow us to design a new family of "competitive allosteric drugs/small molecules" that will have improved selectivity and specificity as compared to their competitive and allosteric counterparts.
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Mittal M, Singh AK, Kumaran S. Structural and biochemical characterization of ligand recognition by CysB, the master regulator of sulfate metabolism. Biochimie 2017; 142:112-124. [PMID: 28838607 DOI: 10.1016/j.biochi.2017.08.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 08/17/2017] [Indexed: 10/19/2022]
Abstract
CysB, a member of LysR-type transcriptional regulators, up-regulates the expression of genes associated with sulfate metabolism and cysteine biosynthesis. CysB is activated under sulfur limiting conditions by O-acetylserine (OAS) and N-acetylserine (NAS), but the activation mechanism of CysB remain unknown. Here, we report four crystal structures of ligand binding domains of CysB (CysB-LBD) in apo form and in complex with sulfate, OAS, and NAS. Our results show that CysB has two distinct allosteric ligand binding sites; a sulfate and NAS specific site-1 and a second, NAS and OAS specific site-2. All three ligands bind through the induced-fit mechanism. Surprisingly, OAS remodels the site-1 by binding to site-2, suggesting that site-1 and site-2 are coupled allosterically. Using DNA binding and site-directed mutagenesis approach, we show that OAS enhances NAS mediated activation and mutation at site-1 has no effect on site-2 mediated OAS activation. Results indicate that inducer binding triggered signals from OAS-Specific site-2 are relayed to DBD through site-1. Together, results presented here suggest that induced-fit binding and allosteric coupling between two ligand binding sites and DBD underlie the key feature of CysB activation. Further, this study provides first structural glimpse into recognition of inducer ligands by CysB and provides a general framework to understand how LTTR family regulators respond to dual activators.
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Babu P, Chittoria RK, Sudhanva HK, Kumaran S, Kumar ES. Radiofrequency-Assisted Body Piercing. J Cutan Aesthet Surg 2017; 10:231-233. [PMID: 29491662 PMCID: PMC5820844 DOI: 10.4103/jcas.jcas_79_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The art of body piercing is ancient; however, nowadays it has evolved into a fashion statement. In the Indian subcontinent, ear and nose piercing hold religious and cultural significance in addition to being done for aesthetic reasons. Body piercing is routinely performed by railroading technique or by piercing guns; many modifications of the technique have emerged. Irrespective of the technique used, the main complications associated are intraoperative bleeding and postoperative infection. To overcome these problems, we describe a novel and simple technique of ear and nose piercing using the radio frequency cautery.
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Singh S, Singh H, Tuknait A, Chaudhary K, Singh B, Kumaran S, Raghava GPS. PEPstrMOD: structure prediction of peptides containing natural, non-natural and modified residues. Biol Direct 2015; 10:73. [PMID: 26690490 PMCID: PMC4687368 DOI: 10.1186/s13062-015-0103-4] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 12/18/2015] [Indexed: 12/16/2022] Open
Abstract
Background In the past, many methods have been developed for peptide tertiary structure prediction but they are limited to peptides having natural amino acids. This study describes a method PEPstrMOD, which is an updated version of PEPstr, developed specifically for predicting the structure of peptides containing natural and non-natural/modified residues. Results PEPstrMOD integrates Forcefield_NCAA and Forcefield_PTM force field libraries to handle 147 non-natural residues and 32 types of post-translational modifications respectively by performing molecular dynamics using AMBER. AMBER was also used to handle other modifications like peptide cyclization, use of D-amino acids and capping of terminal residues. In addition, GROMACS was used to implement 210 non-natural side-chains in peptides using SwissSideChain force field library. We evaluated the performance of PEPstrMOD on three datasets generated from Protein Data Bank; i) ModPep dataset contains 501 non-natural peptides, ii) ModPep16, a subset of ModPep, and iii) CyclicPep contains 34 cyclic peptides. We achieved backbone Root Mean Square Deviation between the actual and predicted structure of peptides in the range of 3.81–4.05 Å. Conclusions In summary, the method PEPstrMOD has been developed that predicts the structure of modified peptide from the sequence/structure given as input. We validated the PEPstrMOD application using a dataset of peptides having non-natural/modified residues. PEPstrMOD offers unique advantages that allow the users to predict the structures of peptides having i) natural residues, ii) non-naturally modified residues, iii) terminal modifications, iv) post-translational modifications, v) D-amino acids, and also allows extended simulation of predicted peptides. This will help the researchers to have prior structural information of modified peptides to further design the peptides for desired therapeutic property. PEPstrMOD is freely available at http://osddlinux.osdd.net/raghava/pepstrmod/. Reviewers This article was reviewed by Prof Michael Gromiha, Dr. Bojan Zagrovic and Dr. Zoltan Gaspari. Electronic supplementary material The online version of this article (doi:10.1186/s13062-015-0103-4) contains supplementary material, which is available to authorized users.
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Singh AK, Singh M, Pandya VK, G L B, Singh V, Ekka MK, Mittal M, Kumaran S. Molecular basis of peptide recognition in metallopeptidase Dug1p from Saccharomyces cerevisiae. Biochemistry 2014; 53:7870-83. [PMID: 25427234 DOI: 10.1021/bi501263u] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dug1p, a M20 family metallopeptidase and human orthologue of carnosinase, hydrolyzes Cys-Gly dipeptide, the last step of glutathione (GSH) degradation in Saccharomyces cerevisiae. Molecular bases of peptide recognition by Dug1p and other M20 family peptidases remain unclear in the absence of structural information about enzyme-peptide complexes. We report the crystal structure of Dug1p at 2.55 Å resolution in complex with a Gly-Cys dipeptide and two Zn(2+) ions. The dipeptide is trapped in the tunnel-like active site; its C-terminus is held by residues at the S1' binding pocket, whereas the S1 pocket coordinates Zn(2+) ions and the N-terminus of the peptide. Superposition with the carnosinase structure shows that peptide mimics the inhibitor bestatin, but active site features are altered upon peptide binding. The space occupied by the N-terminus of bestatin is left unoccupied in the Dug1p structure, suggesting that tripeptides could bind. Modeling of tripeptides into the Dug1p active site showed tripeptides fit well. Guided by the structure and modeling, we examined the ability of Dug1p to hydrolyze tripeptides, and results show that Dug1p hydrolyzes tripeptides selectively. Point mutations of catalytic residues do not abolish the peptide binding but abolish the hydrolytic activity, suggesting a noncooperative mode in peptide recognition. In summary, results reveal that peptides are recognized primarily through their amino and carboxyl termini, but hydrolysis depends on the properties of peptide substrates, dictated by their respective sequences. Structural similarity between the Dug1p-peptide complex and the bestatin-bound complex of CN2 suggests that the Dug1p-peptide structure can be used as a template for designing natural peptide inhibitors.
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Kumaran S, Ravi M, Meenakshi K, Muthukumar D, Swaminathan N, Ravishankar G, Justin Paul G, Manohar G, Murugan S. Pattern of arrhythmias following PTMC – An insight into patient and procedure related factors. Indian Heart J 2014. [DOI: 10.1016/j.ihj.2014.10.388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Kumaran S, Ravi M, Meenakshi K, Muthukumar D, Swaminathan N, Ravishankar G, Justin Paul G, Manohar G, Murugan S, Vengatesan S. Differential pattern of commissural split and it's impact on mitral valve orifice following PTMC. Indian Heart J 2014. [DOI: 10.1016/j.ihj.2014.10.284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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Manjula K, Rajendran K, Eevera T, Kumaran S. QUANTITATIVE ESTIMATION OF LUPEOL AND STIGMASTEROL IN COSTUS IGNEUS BY HIGH-PERFORMANCE THIN-LAYER CHROMATOGRAPHY. J LIQ CHROMATOGR R T 2013. [DOI: 10.1080/10826076.2011.647196] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Sakthivel M, Deivasigamani B, Alagappan KM, Kumaran S, Balamurugan S, Rajasekar T. Seasonal changes in selected immune response of Mystus gulio and Mystus vittatus. JOURNAL OF ENVIRONMENTAL BIOLOGY 2013; 34:37-42. [PMID: 24006805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Estuaries are considered as highly potential area for that including feeding, spawning and nursery rearing of most of the finfishes and shellfishes. In the present investigation, two species of catfish (M. gulio and M. vittatus) were selected to study the impact of season on their immune organs (kidney and spleen) and selected immune response from Vellar estuary. The physico-chemical parameters (pH, temperature, salinity and rainfall) were measured during the sampling period 2009-10. The non-specific immune parameters (WBC count, lysozyme activity and NBT assay) were analyzed. The immune organs (head-kidney and spleen) variation was also observed by histological studies. Our results stated that the WBCs count of M. gulio and M. vittatus increased during summer (10.3 and 10.1 x 10(6) ml(-1)) season and decreased in monsoon (6.8 and 7.0 x 10(6) ml(-1)). In contrast, lysozyme activity was highest in post monsoon (1540 and 1525 U min(-1) ml(-1)) and lowest in summer (1000 and 960 U min(-1) ml(-1)). The activity of NBT was highest in monsoon (0.68 and 0.65 at 540 nm) and lowest in summer (0.012 and 0.2 at 540 nm). The histological observation implies that the cell variations were different in respect to different seasons.
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Biswas D, Pandya V, Singh AK, Mondal AK, Kumaran S. Co-factor binding confers substrate specificity to xylose reductase from Debaryomyces hansenii. PLoS One 2012; 7:e45525. [PMID: 23049810 PMCID: PMC3458928 DOI: 10.1371/journal.pone.0045525] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 08/21/2012] [Indexed: 01/07/2023] Open
Abstract
Binding of substrates into the active site, often through complementarity of shapes and charges, is central to the specificity of an enzyme. In many cases, substrate binding induces conformational changes in the active site, promoting specific interactions between them. In contrast, non-substrates either fail to bind or do not induce the requisite conformational changes upon binding and thus no catalysis occurs. In principle, both lock and key and induced-fit binding can provide specific interactions between the substrate and the enzyme. In this study, we present an interesting case where cofactor binding pre-tunes the active site geometry to recognize only the cognate substrates. We illustrate this principle by studying the substrate binding and kinetic properties of Xylose Reductase from Debaryomyces hansenii (DhXR), an AKR family enzyme which catalyzes the reduction of carbonyl substrates using NADPH as co-factor. DhXR reduces D-xylose with increased specificity and shows no activity towards "non-substrate" sugars like L-rhamnose. Interestingly, apo-DhXR binds to D-xylose and L-rhamnose with similar affinity (K(d)∼5.0-10.0 mM). Crystal structure of apo-DhXR-rhamnose complex shows that L-rhamnose is bound to the active site cavity. L-rhamnose does not bind to holo-DhXR complex and thus, it cannot competitively inhibit D-xylose binding and catalysis even at 4-5 fold molar excess. Comparison of K(d) values with K(m) values reveals that increased specificity for D-xylose is achieved at the cost of moderately reduced affinity. The present work reveals a latent regulatory role for cofactor binding which was previously unknown and suggests that cofactor induced conformational changes may increase the complimentarity between D-xylose and active site similar to specificity achieved through induced-fit mechanism.
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Rajasekar T, Balaji S, Kumaran S, Deivasigamani B, Pugzhavendhan S. Isolation and characterization of Marine fungal metabolites against clinical pathogens. ASIAN PACIFIC JOURNAL OF TROPICAL DISEASE 2012. [DOI: 10.1016/s2222-1808(12)60187-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Kumaran S, Thambiah LJ. Analysis of two different surgical approaches for fractures of the mandibular condyle. Indian J Dent Res 2012; 23:463-8. [DOI: 10.4103/0970-9290.104950] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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Kumaran S, Palani P, Nishanthi R, Srimathi S, Kaviyarasan V. Purification of an Intracellular Fibrinolytic Protease from Ganoderma Lucidum Vk12 and its Susceptibility to Different Enzyme Inhibitors. TROP J PHARM RES 2011. [DOI: 10.4314/tjpr.v10i4.6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Pandya V, Ekka MK, Dutta RK, Kumaran S. Mass spectrometry assay for studying kinetic properties of dipeptidases: characterization of human and yeast dipeptidases. Anal Biochem 2011; 418:134-42. [PMID: 21771575 DOI: 10.1016/j.ab.2011.06.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 06/20/2011] [Accepted: 06/21/2011] [Indexed: 10/18/2022]
Abstract
Chemical modifications of substrate peptides are often necessary to monitor the hydrolysis of small bioactive peptides. We developed an electrospray ionization mass spectrometry (ESI-MS) assay for studying substrate distributions in reaction mixtures and determined steady-state kinetic parameters, the Michaelis-Menten constant (K(m)), and catalytic turnover rate (V(max)/[E](t)) for three metallodipeptidases: two carnosinases (CN1 and CN2) from human and Dug1p from yeast. The turnover rate (V(max)/[E](t)) of CN1 and CN2 determined at pH 8.0 (112.3 and 19.5s(-1), respectively) suggested that CN1 is approximately 6-fold more efficient. The turnover rate of Dug1p for Cys-Gly dipeptide at pH 8.0 was found to be slightly lower (73.8s(-1)). In addition, we determined kinetic parameters of CN2 at pH 9.2 and found that the turnover rate was increased by 4-fold with no significant change in the K(m). Kinetic parameters obtained by the ESI-MS method are consistent with results of a reverse-phase high-performance liquid chromatography (RP-HPLC)-based assay. Furthermore, we used tandem MS (MS/MS) analyses to characterize carnosine and measured its levels in CHO cell lines in a time-dependent manner. The ESI-MS method developed here obviates the need for substrate modification and provides a less laborious, accurate, and rapid assay for studying kinetic properties of dipeptidases in vitro as well as in vivo.
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